Since it was launched in 2006 the New Horizons spaceship has been speeding away. Scientists using the Alice UV imager on board New Horizons have been waiting for 15 years to get enough distance from the Sun to measure the brightness of the stars in the sky. This has never been measured accurately.
The author of a new paper said that moving away from the Sun made them less blinded by the solar component of the background. This has been guessed at by the astronomer for a long time. We now have a more precise number.
During the mission, Alice was used to make observations of the Lyman-alpha background, which included three times during the cruise to Pluto, another just one month prior to the mission's flyby of Pluto, and five times.
The galactic component of the Lyman-alpha background is 20 times less bright than the Earth's.
There are instruments on the new mission. The composition of atmosphere and search for atmosphere around Charon have been studied using the Alice UV imager. The Southwest Research Institute is a part of NASA.
Scientists have only been able to make estimates of how pervasive the ultraviolet background is for the last 60 years.
The tenuous wind of hydrogen atoms can be measured using the Lyman-alpha ultraviolet background glow. Astronomers can see in the dark if they study this wavelength of light. Observational scientists have been able to map out the distribution of matter in the universe using an instrument similar to Alice on the Lunar Reconnaissance Orbiter.
A map shows the permanently shadowed regions that cover 3 percent of the moon's south pole. The LRO mission was credited by NASA.
The background in space is caused by hot regions around massive stars which ionize all the matter near them. There are hydrogen atoms between the stars. Most of the solar system is dominated by the sun's light.
The night sky would never get darker than twilight if we could see the Lyman-alpha background. We weren't sure how much the Milky Way galaxy contributed to its overall brightness. It is like standing near a streetlamp on a foggy night. The fog makes it hard to see anything else.
The fainter components of the signal from the nearby regions of the Milky Way are easier to see than the scattered sunlight component. The team said in their paper that a more precise measurement will help them understand the nearby regions of the Milky Way.
Alan Stern, the principal investigator of New Horizons, said that it was a great resource for the exploration of the Kuiper Belt, but also to understand more about our universe and even the universe beyond our galaxy.
The false-color map shows several scans of the Lyman-alpha background over the sky obtained by the Alice ultraviolet spectrograph when it was 45AU from the Sun. The data agrees with the model of the solar component of the background to which a constant brightness from the Milky Way has been added. There is an orange dot on the background near the Sun. Credit: SwRI
